i too owned early mon 40’s -- in the 2003/4 time frame iirc (these were the original monitors, grey britex cabinets with side handles)... had them for about a year, sold my spendor sp100’s to get them -- a big mistake which i continually regretted till last year, when i finally managed to get another set of 100’s back
i had roger modjeski’s wonderful rm9-2 tube amp and an aragon 8008 ss amp back then... neither did well with the 40’s, the tube amp left the bass overblown and uncontrolled... the aragon took care of that but flattened the imaging and made the treble way too ’hifi’
so i too sold the 40’s after a year or so, went to big proac’s, which i just loved...
the mon 40’s certainly need a lot of amplifier bass damping factor, and also, placement is quite critical for finding the right bass balance in room (well well away from boundaries, tough for such a humongous box)... but then the mids and treble are quite revealing, the solid stateness of the powerhouse aragon called too much attention to itself, and not in a good way
all this was a real lesson in getting the room/speaker placement/amp combo implemented just right... learned the hard way...